1. Field of the Invention
This invention relates to methods and devices for reducing drag on blunt-body vehicles.
2. Description of the Related Art
Current proposed shapes for single-stage-to-orbit vehicles like the Lockheed-Martin X-33 and “Venture-Star” reusable launch vehicle (RLV) have extremely large base areas when compared to previous hypersonic vehicle designs. As a result, base drag, especially in the transonic flight regime, is expected to be very large, and will likely dominate or overwhelm all other factors relevant to the vehicle performance. Excessive base drag could seriously limit the range of available landing sites for the “Venture Star” and will reduce payload capability. The unique configuration of Lockheed-Martin RLV with its very large base are and relatively low forebody drag, offers the potential for a large increase in overall vehicle performance, if the base drag can be reduced significantly.
There have been previous attempts to generally address the issue of drag reduction by altering the surface of a vehicle. 
U.S. Pat. No. 4,907,765 discloses a wall having a drag-reducing configuration comprising a wall structure with sharp edged ridges separated by valleys that have drag reducing characteristics.
U.S. Pat. No. 5,378,524 discloses a vehicle with an outer surface that includes a matrix of cavities. The vehicle is selected from the group consisting of automobile, airplane and boat.
U.S. Pat. No. 5,346,745 discloses a plurality of surface elements arranged in rows on the surface of an object, with the surface elements of each row being arranged generally orthogonal to the direction of relative motion of the object. Each surface element includes means defining a cavity, and the cavities are interconnected by means of passageways to facilitate fluid communication therebetween. The passageways facilitate equalization of pressure between the cavities of the surface elements in each row, which ultimately results in reducing turbulence around the object.
U.S. Pat. No. 2,261,558 discloses providing recesses of various sorts and shapes on the surface of a vehicle, such as will minimize the air and water resistance offered by the vehicle, especially when proceeding at relatively high speeds.
U.S. Pat. No. 5,171,623 discloses drag-reducing surface depressions that are shaped like sections of truncated cones, or hexagonal prisms, geodesic domes, and that cover the entire surface of the body of the vehicle.
What each of these prior art approaches has in common is that they use depressions in the vehicle surface to reduce drag at the locations of the depressions. However, none of these approaches address the issues peculiar to blunt-based vehicles with extremely large base areas, and none disclose reducing overall vehicle drag by increasing drag at particular areas of a  vehicle. Therefore, a need exists for a method of reducing drag in a blunt-based vehicle with an extremely large base area that is effective, easy to implement, applicable to all types of blunt-based vehicles at all speeds, and does not decrease the inherent structural integrity of the vehicle